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Sökning: WFRF:(Norris John E.)

  • Resultat 1-15 av 15
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1.
  • 2021
  • swepub:Mat__t
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2.
  • Kanai, M, et al. (författare)
  • 2023
  • swepub:Mat__t
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3.
  • 2019
  • Tidskriftsartikel (refereegranskat)
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4.
  • Feitosa, Mary F., et al. (författare)
  • Novel genetic associations for blood pressure identified via gene-alcohol interaction in up to 570K individuals across multiple ancestries
  • 2018
  • Ingår i: PLOS ONE. - : Public library science. - 1932-6203. ; 13:6
  • Tidskriftsartikel (refereegranskat)abstract
    • Heavy alcohol consumption is an established risk factor for hypertension; the mechanism by which alcohol consumption impact blood pressure (BP) regulation remains unknown. We hypothesized that a genome-wide association study accounting for gene-alcohol consumption interaction for BP might identify additional BP loci and contribute to the understanding of alcohol-related BP regulation. We conducted a large two-stage investigation incorporating joint testing of main genetic effects and single nucleotide variant (SNV)-alcohol consumption interactions. In Stage 1, genome-wide discovery meta-analyses in approximate to 131 K individuals across several ancestry groups yielded 3,514 SNVs (245 loci) with suggestive evidence of association (P <1.0 x 10(-5)). In Stage 2, these SNVs were tested for independent external replication in individuals across multiple ancestries. We identified and replicated (at Bonferroni correction threshold) five novel BP loci (380 SNVs in 21 genes) and 49 previously reported BP loci (2,159 SNVs in 109 genes) in European ancestry, and in multi-ancestry meta-analyses (P < 5.0 x 10(-8)). For African ancestry samples, we detected 18 potentially novel BP loci (P< 5.0 x 10(-8)) in Stage 1 that warrant further replication. Additionally, correlated meta-analysis identified eight novel BP loci (11 genes). Several genes in these loci (e.g., PINX1, GATA4, BLK, FTO and GABBR2 have been previously reported to be associated with alcohol consumption. These findings provide insights into the role of alcohol consumption in the genetic architecture of hypertension.
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5.
  • de las Fuentes, Lisa, et al. (författare)
  • Gene-educational attainment interactions in a multi-ancestry genome-wide meta-analysis identify novel blood pressure loci
  • 2021
  • Ingår i: Molecular Psychiatry. - : Springer Nature. - 1359-4184 .- 1476-5578. ; 26:6, s. 2111-2125
  • Tidskriftsartikel (refereegranskat)abstract
    • Educational attainment is widely used as a surrogate for socioeconomic status (SES). Low SES is a risk factor for hypertension and high blood pressure (BP). To identify novel BP loci, we performed multi-ancestry meta-analyses accounting for gene-educational attainment interactions using two variables, “Some College” (yes/no) and “Graduated College” (yes/no). Interactions were evaluated using both a 1 degree of freedom (DF) interaction term and a 2DF joint test of genetic and interaction effects. Analyses were performed for systolic BP, diastolic BP, mean arterial pressure, and pulse pressure. We pursued genome-wide interrogation in Stage 1 studies (N = 117 438) and follow-up on promising variants in Stage 2 studies (N = 293 787) in five ancestry groups. Through combined meta-analyses of Stages 1 and 2, we identified 84 known and 18 novel BP loci at genome-wide significance level (P < 5 × 10-8). Two novel loci were identified based on the 1DF test of interaction with educational attainment, while the remaining 16 loci were identified through the 2DF joint test of genetic and interaction effects. Ten novel loci were identified in individuals of African ancestry. Several novel loci show strong biological plausibility since they involve physiologic systems implicated in BP regulation. They include genes involved in the central nervous system-adrenal signaling axis (ZDHHC17, CADPS, PIK3C2G), vascular structure and function (GNB3, CDON), and renal function (HAS2 and HAS2-AS1, SLIT3). Collectively, these findings suggest a role of educational attainment or SES in further dissection of the genetic architecture of BP.
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7.
  • Dalton, April S., et al. (författare)
  • Deglaciation of the north American ice sheet complex in calendar years based on a comprehensive database of chronological data: NADI-1
  • 2023
  • Ingår i: QUATERNARY SCIENCE REVIEWS. - 0277-3791 .- 1873-457X. ; 321
  • Tidskriftsartikel (refereegranskat)abstract
    • The most recent deglaciation of the North American Ice Sheet Complex (NAISC: comprising the Innuitian, Cordilleran, and Laurentide ice sheets) offers a broad perspective from which to analyze the timing and rate of ice retreat, deglacial sea-level rise, and abrupt climate change events. Previous efforts to portray the retreat of the NAISC have been focused largely on minimum-limiting radiocarbon ages and ice margin location(s) tied to deglacial landforms that were not, for the most part, chronologically constrained. Here, we present the first version of North American Deglaciation Isochrones (NADI-1) spanning 25 to 1 ka in calendar years before present. Key new features of this work are (i) the incorporation of cosmogenic nuclide data, which offer a direct constraint on the timing of ice recession; (ii) presentation of all data and time-steps in calendar years; (iii) optimal, minimum, and maximum ice extents for each time-step that are designed to capture uncertainties in the ice margin position, and; (iv) extensive documentation and justification for the placement of each ice margin. Our data compilation includes 2229 measurements of Be-10, 459 measurements of Al-26 and 35 measurements of Cl-36 from a variety of settings, including boulders, bedrock surfaces, cobbles, pebbles, and sediments. We also updated a previous radiocarbon dataset (n = 4947), assembled luminescence ages (n = 397) and gathered uranium-series data (n = 2). After scrutiny of the geochronological dataset, we consider >90% of data to be reliable or likely reliable. Key findings include (i) a highly asynchronous maximum glacial extent in North America, occurring as early as 27 ka to as late as 17 ka, within and between ice sheets. In most marine realms, extension of the ice margin to the continental shelf break at 25 ka is somewhat speculative because it is based on undated and spatially scattered ice stream and geomorphic evidence; (ii) detachment of the Laurentide and Cordilleran ice sheets took place gradually via southerly and northerly 'unzipping' of the ice masses, starting at 17.5 ka and ending around 14 ka; (iii) the final deglaciation of Hudson Bay began at 8.5 ka, with the collapse completed by 8 ka. The maximum extent of ice during the last glaciation occurred at 22 ka and covered 15,470,000 km(2). All North American ice sheets merged at 22 ka for the first time in the Quaternary. The highly asynchronous Last Glacial Maximum in North America means that our isochrones (starting at 25 ka) capture ice advance across some areas, which is based on limited evidence and is therefore somewhat speculative. In the Supplementary Data, the complete NADI-1 chronology is available in PDF, GIF and shapefile format, together with additional visualizations and spreadsheets of geochronological data. The NADI-1 shapefiles are also available at https://doi.org/10.5281/zenodo.8161764.
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8.
  • Bessell, Michael S., et al. (författare)
  • Nucleosynthesis in a Primordial Supernova : Carbon and Oxygen Abundances in SMSS J031300.36-670839.3
  • 2015
  • Ingår i: Astrophysical Journal Letters. - 2041-8205 .- 2041-8213. ; 806:1
  • Tidskriftsartikel (refereegranskat)abstract
    • SMSS J031300.36-670839.3 (hereafter SM0313-6708) is a sub-giant halo star, with no detectable Fe lines and large overabundances of C and Mg relative to Ca. We obtained Very Large Telescope-Ultraviolet and Visual Echelle Spectrograph (UVES) spectra extending to 3060 angstrom showing strong OH A-X band lines enabling an oxygen abundance to be derived. The OH A-X band lines in SM0313-6708 are much stronger than the CH C-X band lines. Spectrum synthesis fits indicate an [O/C] ratio of 0.02 +/- 0.175. Our high signal-to-noise ratio UVES data also enabled us to lower the Fe abundance limit to [Fe/H](< 3D >,NLTE) < -7.52 (3 sigma). These data support our previous suggestion that the star formed from the iron-poor ejecta of a single massive star Population III supernova.
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9.
  • Frebel, Anna, et al. (författare)
  • Chemical abundance analysis of the extremely metal-poor star HE 1300+0157
  • 2007
  • Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 658:1, s. 534-552
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a detailed chemical abundance analysis of HE 1300+0157, a subgiant with Fe/H = -3.9. Froma high-resolution, high-S/N Subaru HDS spectrum we find the star to be enriched in C ([C/Fe](1D) similar to +1.4) and O ([O/Fe](1D) similar to +1.8). With the exception of these species, HE 1300+0157 exhibits an elemental abundance pattern similar to that found in many other very and extremely metal-poor stars. The Li abundance is lower than the Spite plateau value, in agreement with expectation for its evolutionary status. Of particular interest, no neutron-capture elements are detected in HE 1300+0157. This type of abundance pattern has been found by recent studies in several other metal-poor giants. We suggest that HE 1300+0157 is an unevolved example of this group of stars, which exhibit high C abundances together with low (or absent) abundances of neutron-capture elements (CEMP-no). Several potential enrichment scenarios are presented. The nondetection of neutron-capture elements including Sr, Ba, and Pb suggests that the carbon excess observed in HE 1300+0157 is not due to mass transfer across a binary system. Such a scenario is applied to carbon-rich objects with excesses of s-process elements. The normal observed Li abundance supports this interpretation. Most likely, the high levels of C and O were produced prior to the birth of this star. It remains unclear whether a single faint SN is responsible for its overall chemical pattern, or whether one requires a superposition of yields from a massive Population III object and a hypernova. These scenarios provide important information on the C production in the early universe and on the formation of C-rich stars in the early Galaxy.
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10.
  • Frebel, Anna, et al. (författare)
  • Discovery of HE 1523-0901, a strongly r-process-enhanced metal-poor star with detected uranium
  • 2007
  • Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 660:2, s. L117-L120
  • Tidskriftsartikel (refereegranskat)abstract
    • We present age estimates for the newly discovered, very r-process-enhanced metal-poor star HE 1523 - 0901 ([Fe/H] = -2.95) based on the radioactive decay of Th and U. The bright (V = 11.1) giant was found among a sample of bright metal-poor stars selected from the Hamburg/ESO Survey. From an abundance analysis of a high-resolution (R = 75,000) VLT/UVES spectrum, we find HE 1523 - 0901 to be strongly overabundant in r- process elements ([r/Fe] = 1.8). The abundances of heavy neutron-capture elements (Z > 56) measured in HE 1523 - 0901 match the scaled solar r- process pattern extremely well. We detect the strongest optical U line at 3859.57 angstrom. For the first time, we are able to employ several different chronometers, such as the U/Th, U/Ir, Th/ Eu, and Th/Os ratios to measure the age of a star. The weighted average age of HE 1523 - 0901 is 13.2 Gyr. Several sources of uncertainties are assessed in detail.
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11.
  • Goswami, Aruna, et al. (författare)
  • A high-resolution spectral analysis of three carbon-enhanced metal-poor stars
  • 2006
  • Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 372:1, s. 343-356
  • Tidskriftsartikel (refereegranskat)abstract
    • We present results of an analysis of high-resolution spectra (R similar to 50 000), obtained with the Subaru Telescope High Dispersion Spectrograph, of two carbon-enhanced metal-poor (CEMP) stars selected from the Hamburg/European Southern Observatory prism survey, HE 1305+0007 and HE 1152-0355, and of the classical CH star HD 5223. All these stars have relatively low effective temperatures (4000-4750 K) and high carbon abundances, which result in the presence of very strong molecular carbon bands in their spectra. The stellar atmospheric parameters for these stars indicate that they all have surface gravities consistent with a present location on the red giant branch, and metallicities of [Fe/H] = -2.0 (HE 1305+0007, HD 5223) and [Fe/H] = -1.3 (HE 1152-0355). In addition to their large enhancements of carbon ([C/Fe] = +1.8, +1.6, and +0.6, respectively), all three stars exhibit strong enhancements of the s-process elements relative to iron. HE 1305+0007 exhibits a large enhancement of the third-peak s-process element, lead, with [Pb/Fe] = +2.37, as well as a high abundance of the r-process element europium, [Eu/Fe] = +1.97. The second-peak s-process elements, Ba, La, Ce, Nd and Sm, are found to be more enhanced than the first-peak s-process elements Zr, Sr and Y. Thus, HE 1305+0007 joins the growing class of the so-called 'Lead stars', and also the class of objects that exhibit the presence of both r- and s-process elements, the CEMP-r/s stars. The large enhancements of neutron-capture (n-capture) elements exhibited by HE 1152-0355 and HD 5223 are more consistent with the abundance patterns generally noticed in CH stars, essentially arising from pure s-process nucleosynthesis. The elemental abundance distributions observed in these stars are discussed in light of existing theories of CH star formation, as well as the suggested formation scenarios of the CEMP-r/s group.
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12.
  • Jacobson, Heather R., et al. (författare)
  • High-Resolution Spectroscopic Study of Extremely Metal-Poor Star Candidates from the Skymapper Survey
  • 2015
  • Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 807:2
  • Tidskriftsartikel (refereegranskat)abstract
    • The SkyMapper Southern Sky Survey is carrying out a search for the most metal-poor stars in the Galaxy. It identifies candidates by way of its unique filter set which allows for estimation of stellar atmospheric parameters. The set includes a narrow filter centered on the Ca II K 3933 angstrom line, enabling a robust estimate of stellar metallicity. Promising candidates are then confirmed with spectroscopy. We present the analysis of Magellan Inamori Kyocera Echelle high-resolution spectroscopy of 122 metal-poor stars found by SkyMapper in the first two years of commissioning observations. Forty-one stars have [Fe/H] <= -3.0. Nine have [Fe/H] <= -3.5, with three at [Fe/H] similar to -4. A 1D LTE abundance analysis of the elements Li, C, Na, Mg, Al, Si, Ca, Sc, Ti, Cr, Mn, Co, Ni, Zn, Sr, Ba, and Eu shows these stars have [X/Fe] ratios typical of other halo stars. One star with low [X/Fe] values appears to be "Fe-enhanced," while another star has an extremely large [Sr/Ba] ratio: >2. Only one other star is known to have a comparable value. Seven stars are "CEMP-no" stars ([C/Fe] > 0.7, [Ba/Fe] < 0). 21 stars exhibit mild r-process element enhancements (0.3 <= [Eu/Fe] < 1.0), while four stars have [Eu/Fe] >= 1.0. These results demonstrate the ability to identify extremely metal-poor stars from SkyMapper photometry, pointing to increased sample sizes and a better characterization of the metal-poor tail of the halo metallicity distribution function in the future.
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13.
  • Norris, John E., et al. (författare)
  • HE 0557-4840 : Ultra-metal-poor and carbon-rich
  • 2007
  • Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 670:1, s. 774-788
  • Tidskriftsartikel (refereegranskat)abstract
    • We report the discovery and high-resolution, high-S/N spectroscopic analysis of the ultra-metal-poor red giant HE 0557-4840, which is the third most heavy-element-deficient star currently known. Its atmospheric parameters are Teff=4900 K, logg=2.2, and [Fe/H]=-4.75. This brings the number of stars with [Fe/H]<-4.0 to three, and the discovery of HE 0557-4840 suggests that the metallicity distribution function of the Galactic halo does not have a ``gap'' between [Fe/H]=-4.0, where several stars are known, and the two most metal-poor stars, at [Fe/H]~-5.3. HE 0557-4840 is carbon rich ([C/Fe]=+1.6), a property shared by all three objects with [Fe/H]<-4.0, suggesting that the well-known increase of carbon relative to iron with decreasing [Fe/H] reaches its logical conclusion (ubiquitous carbon richness) at lowest abundance. We also present abundances (nine) and limits (nine) for a further 18 elements. For species having well-measured abundances or strong upper limits, HE 0557-4840 is ``normal'' in comparison with the bulk of the stellar population at [Fe/H]~-4.0, with the possible exception of Co. We discuss the implications of these results for chemical enrichment at the earliest times, in the context of single- (``mixing and fallback'') and two-component enrichment models. While neither offers a clear solution, the latter appears closer to the mark. Further data are required to determine the oxygen abundance and improve that of Co, and hence more strongly constrain the origin of this object. Based on observations collected at ANU's 2.3 m telescope on Siding Spring Mountain, Australia, and European Southern Observatory, Paranal, Chile (proposal 276.D-5041).
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14.
  • Norris, John E., et al. (författare)
  • The oxygen abundance of the ultra-metal-poor star HE 0557-4840
  • 2012
  • Ingår i: Astrophysical Journal. - : Institute of Physics (IOP). - 0004-637X .- 1538-4357. ; 753:2, s. 150-
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a high-resolution ultraviolet (UV) spectrum of the ultra-metal-poor (UMP) carbon-enhanced red giant HE 0557-4840 (T-eff/log g/[Fe/H] = 4900/2.2/-4.8). Combining these data with earlier observations, the radial velocity is 212.0 +/- 0.4 km s(-1), with no evidence of variability during 2006 February to 2007 December. One-dimensional (1D) LTE model-atmosphere analysis of UV Fe and CH lines confirms the iron and carbon abundances obtained previously ([Fe/H] = -4.8 and [C/Fe](1D) = +1.7), and places a more stringent limit on nitrogen abundance of [N/Fe](1D) < +1.0. Analysis of the UV OH lines yields [O/Fe](1D) = +2.3 +/- 0.4. When corrections are made for three-dimensional (3D) effects we obtain [C/Fe](3D) = +1.1, [N/Fe](3D) < +0.1, and [O/Fe](3D) = +1.4. Comparison of the abundances of HE 0557-4840 with those of supernova models of Nomoto et al. and Joggerst et al. suggests that none is able to explain fully the observed abundance pattern. For HE 0557-4840, the Frebel et al. transition discriminant D-trans(= log(10([C/H]) + 0.3 x 10([O/H])) = -3.4 +/- 0.2, consistent with fine-structure transitions of C II and O I being a major cooling mechanism of star-forming regions at the earliest times. Of the four stars known to have [Fe/H] less than or similar to -4.3, three are strongly carbon and oxygen enhanced. If the suggestion by Caffau et al. that SDSS J102915+172927 ([Fe/H] = -4.7) does not belong to the class of C-rich, O-rich, UMP stars is supported by future similar discoveries, one will need to consider multiple channels for the production of stars having [Fe/H] less than or similar to -4.3.
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15.
  • Yong, David, et al. (författare)
  • The most metal-poor stars. III. The metallicity distribution function and carbon-enhanced metal-poor fraction
  • 2013
  • Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 762:1, s. 27-
  • Tidskriftsartikel (refereegranskat)abstract
    • We examine the metallicity distribution function (MDF) and fraction of carbon-enhanced metal-poor (CEMP) stars in a sample that includes 86 stars with [Fe/H] <= -3.0, based on high-resolution, high signal-to-noise spectroscopy, of which some 32 objects lie below [Fe/H] = -3.5. After accounting for the completeness function, the "corrected" MDF does not exhibit the sudden drop at [Fe/H] = -3.6 that was found in recent samples of dwarfs and giants from the Hamburg/ESO survey. Rather, the MDF decreases smoothly down to [Fe/H] = -4.1. Similar results are obtained from the "raw" MDF. We find that the fraction of CEMP objects below [Fe/H] = -3.0 is 23% +/- 6% and 32% +/- 8% when adopting the Beers & Christlieb and Aoki et al. CEMP definitions, respectively. The former value is in fair agreement with some previous measurements, which adopt the Beers & Christlieb criterion.
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